Approximately 175 years ago, the first technologies for the capture and reproduction of individual still images were developed (e.g., the Daguerreotype process). Such technology, called “photography,” was based on photosensitive and irreversible chemical reactions. Then, approximately 125 years ago, technologies were developed to capture and reproduce scenes with motion—so-called “motion pictures.”
A motion picture camera relies upon the capture of a quick succession of still images, while recording the original scene. For example, the sequence of still images can be captured at a rate of approximately 30 per second. The sequence of still images is then chemically developed, using essentially the same technology by which photographic still images had been produced. The images captured are then displayed in the same sequence, and at the same speed, at which they had been captured. It was found that this sequential display of images is experienced, by the human visual system, as something very similar to a still image—except the “picture” also reproduced, realistically, motion present in the original scene.
These two technologies, photography and motion pictures, represented the foundation of visual media. More generally, we can refer to photography as the foundation, and initial technological platform, for what we can refer to as “still image visual media.” Similarly, we can refer to motion pictures as the foundation, and initial technological platform, for what we can refer to as “moving image visual media.” Since the introduction of still image and moving image visual media, and until about 20 years ago (i.e., a period of about 100 years), the development of these two types of media can be characterized as being almost exclusively focused on the following two broad goals:                Improving the channels, by which such visual media can be distributed (e.g., making the distribution faster, and less expensive).        Improving the visual quality of the visual media (e.g., adding the ability to reproduce color, and improving resolution).        
The last 20 years of visual media development can be differentiated from the previous 100 years by the confluence of two new developments:                Widespread availability of computer networking technologies (e.g., the Internet, along with the various wired and wireless mediums by which to achieve connectivity).        Widespread availability of digital imaging technologies, for both still image and moving image visual media.        
The confluence of these two developments has resulted in something of a revolution, with regard to visual media, that can be referred to herein as the “digital imaging revolution.”
The digital imaging revolution has so successfully satisfied the long-term goals listed above (distribution that is rapid and inexpensive; images distributed are of high-quality), that privacy and control have now become major concerns.
Other than its capacity to act as a phone (a capability that continues to become less and less important), the so-called “smart phone” is really a powerful and pocket-sized computer. They are almost always equipped with a camera, that can take still images or video. Any images or video captured can then be distributed, very quickly, because almost all smart phones are now provided with a ubiquitous, and relatively high speed, Internet connection.
In sum, a smart phone delivers a kind of capacity, for the creation and distribution of visual media, which, just 35 years ago, would require the facilities of a television network studio.
Like any major brand of computer, a smart phone can be loaded with a wide variety of application software (with such application software, in smart phone jargon, generally referred to as “apps”).
The increasing concern among smart phone users, regarding privacy and control, is evidenced by the popularity of apps that attempt to make visual media sharing more ephemeral and temporary. For example, the app SNAPCHAT is extremely popular. A major feature of Snapchat is that the pictures shared through it can only be seen for a limited time period, and are then automatically deleted.
However, there can be a serious vulnerability for such privacy-enhancing apps. The operating system (OS), of essentially all smart phones, includes a capability for the taking of “screenshots.” Because the screenshot facility is provided at the OS level, it is available to a smart phone user regardless of the particular app, he or she may be using.
Thus, even if an app (e.g., Snapchat) deletes an image shortly after it becomes viewable, the recipient of the image can take a screenshot of the picture, and thereby circumvent the intended privacy and control. The screenshot facility is of particular concern on smart phones that run APPLE's iOS, because, under iOS, apps cannot disable the screenshot facility.
It would therefore be desirable to be able to control the display of images, such that the screenshot facility is a lesser vulnerability, for privacy and control.